'requested item "......" does not exist'
Analysis


  Python module can't be imported - object 'Cube', controller 'Python': KeyError: 'requested item "run" does not exist'


This means you misconfigured the Python controller.

Either you use script mode and you refer to an not existing text block called "run" (the field should have red background).

Or you use module mode and you did not mention what file contains your code.

E.g. your code is called arduino.py. You can set up this line: arduino.applyRotation. 

The BGE will look for arduino.py and check if it finds a function applyRotation.

arduino.py

import bge 

def applyRotation(controller):
    sensor = controller.sensors["run"]
    if sensor.positive:
        ...


Solution

Ensure the file and the function inside of it can be found.

Hint:

If you want to use the module mode ensure to retrieve the controller inside of the called function. Otherwise you get unwanted side effects.